<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-wid
    th, initial0-scale=1.0">
    <title>Document</title>
    <style>
      *{
          margin: 0;
          padding: 0;
      }  
      body{
          display: flex;
          flex-wrap: wrap;
      }

      div{
          height: 100px;
          background: yellow;
          border:  2px solid red;
          box-sizing: border-box;
          width: 33.3333%;
      }

      @media screen and (orientation:portrait) {
          div{
              width: 33.33%;
          }
      }
     @media screen and (orientation:landscape) {
         div{
             width: 20%;
         }
     }
    </style>
</head>
<body>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>
    <div></div>   
</body>
</html>